Stratolaunch founder Paul Allen posted a video of the supersized ‘space plane’ out on the runway for a test ride this week.

Allen said that the Stratolaunch reached speeds of 46 miles per hour earlier this week, beating the taxi speed of 28 mph that it reached in December.

Stratolaunch is the world’s largest aircraft by wingspan and is the largest all-composite plane ever built. The company’s stated aim is to “make access to space more convenient, reliable, and routine”. Stratolaunch is currently under construction at the Mojave Air & Space Port in California, and is slated to be fully operational by the end of 2020.